1. Field of the Invention
The present invention generally relates to thermal process apparatuses for semiconductor devices, and more particularly, to a thermal process apparatus for a semiconductor substrate which can be used for measuring of a temperature as to a semiconductor substrate with high precision.
2. Description of the Related Art
FIG. 1 is a view showing a structure of a conventional rapid thermal process apparatus which is used as a chemical vapor deposition (CVD) apparatus or an annealing apparatus for manufacturing a semiconductor integrated circuit. As shown in FIG. 1, the rapid thermal process apparatus includes a heating source 1, a guard ring 5, a quartz rod 7, an optical fiber 9 and a radiation thermometer 11. The heating source 1 includes a halogen lamp. The guard ring 5 supports a wafer 3 which is an object for heating process. The quartz rod 7 is provided in a bottom plate 8. The optical fiber 9 transmits a radiation beam radiated from the wafer 3 and detected by the quartz rod 7. The radiation thermometer 11 is connected with the optical fiber 9.
With the above-mentioned structure of the rapid thermal process apparatus, the wafer 3 supported by the guard ring 5 is heated by the radiation beam radiated from the halogen lamp. The wafer 3 is heated from a room temperature to for instance 1000xc2x0 C., with a rate of 100xc2x0 C./sec for instance.
The radiation beam radiated from the wafer 3 is detected by the quartz rod 7. The temperature of the wafer 3 is detected by the radiation thermometer 11 on the basis of the detected beam.
However, the conventional rapid thermal process apparatus having the above-mentioned structure has disadvantages. That is, the temperature of the wafer 3 is detected based on the radiation beam detected by the quartz rod 7. Therefore, as shown in FIG. 1, a stray light 10, which is a part of the radiation beam radiated from the heating source 1, may be incident on the quartz rod 7. That is, the stray light 10 may be reflected multiply between the wafer 3 and the bottom plate 8 and may be incident on the quartz rod 7. As a result, a light other than the radiation beam radiated from the wafer 3 is also detected by the quartz rod 7. This causes a problem in that it is not possible to detect the temperature of the wafer 3 reliably.
Also, an area of the multiple reflection of the stray light is not fixed. Hence, it is not possible to make an accurate correction formula for a radiation ratio.
Accordingly, it is a general object of the present invention is to provide a novel and useful thermal process apparatus for a semiconductor substrate in which one or more of the problems described above are eliminated.
Another and more specific object of the present invention is to provide a thermal process apparatus for a semiconductor substrate which can be used for measuring a temperature of a semiconductor substrate with high accuracy.
The above objects of the present invention are achieved by a thermal process apparatus for a semiconductor substrate, including a heating source heating the semiconductor substrate by irradiating a light on one side of the semiconductor substrate, a reflection plate facing to the semiconductor substrate in a state where a reflection cavity is formed with another side of the semiconductor substrate, a thermometer having a light-receiving part provided on the refection plate so as to measure a temperature of the semiconductor substrate by catching a radiation beam from the semiconductor substrate heated by the heating source by the light-receiving part; and light absorption means provided around the light-receiving part for absorbing a diffuse reflection light generated in the reflection cavity.
According to the above invention, it is possible to absorb the diffuse reflection light, namely a stray light, by the light absorption means, prior to the light being incident on the light-receiving part of the thermometer. Hence, it is possible to avoid that the diffuse reflection light is incident on the temperature measure means.
The light absorption means may include a concave part forming a black body, so that the diffuse reflection light can be absorbed effectively.
The concave part may have an opening width whose value is greater than D*tan xcex8, where sin xcex8 is defined as a numerical aperture in a vacuum when the light-receiving part catches the light and D is defined as a distance between the concave part and the semiconductor substrate. The concave part may have an opening whose cross sectional configuration is a triangle, a quadrilateral, a hexagonal, or any other polygon. In this case, the opening configuration is regarded as a circle, thereby its opening width is calculated as described above.
The concave part may be provided in a distance of an even number multiple of D*tan xcex8 from the light-receiving part, where sin xcex8 is defined as a numerical aperture in a vacuum when the light-receiving part catches the light and D is defined as a distance between the concave part and the semiconductor substrate.
The concave part may be provided in a distance of r/tan xcex8 and under the semiconductor substrate, where sin xcex8 is defined as a numerical aperture in a vacuum when the light-receiving part catches the light and r is defined as a value of a radius of an opening of the light-receiving part.
Furthermore, the light absorption means may include a groove having a designated radius and depth, so that the diffuse reflection light can be confined in the groove. Hence, it is possible to avoid that the diffuse reflection light is incident on the light-receiving part.
Also, the light absorption means may include a projection body having a groove, a distance between the top surface of the projection body and the semiconductor substrate being smaller than a distance between the light-receiving part and the semiconductor substrate.
Other objects, features, and advantages of the present invention will be more apparent from the following detailed description when read in conjunction with the accompanying drawings.